<meta name="viewport" content="width=device-width" />
<img id="pic" onclick="kaiDeng()" src="pic_bulboff.gif" />

<script>
var i = 1;
function kaiDeng(){
  if(i==1){
    pic.src = "pic_bulbon.gif";
    i = 0;
  }else{
    pic.src = "pic_bulboff.gif";
    i = 1;
  }
}
</script>